1. Field of the Invention
Aspects of the present invention relate to a catalyst coated electrolyte membrane, a fuel cell including the same, and a method of preparing the catalyst coated electrolyte membrane, and more particularly, to a catalyst coated electrolyte membrane with improved performance and durability in which micro cracks of an electrode catalyst layer are minimized and thus the resistance between the electrode catalyst layer and an electrolyte membrane can be minimized, and crossover of a fuel to a cathode electrode is minimized, a fuel cell including the same, and a method of preparing the catalyst coated electrolyte membrane.
2. Description of the Related Art
Fuel cells are a type of a power generating system that directly converts a chemical energy of hydrogen contained in hydrocarbons, such as methanol, ethanol, and natural gas, and oxygen into an electrical energy.
A fuel cell system has a basic structure of a fuel cell stack, a fuel processor (FP), a fuel tank, a fuel pump etc. A fuel cell stack is a main body of a fuel cell, and is formed by stacking a few or tens of unit cells, each of which includes an electrolyte membrane electrode assembly (MEA) and a separator or bipolar plate.
An MEA includes an anode diffusion electrode, a cathode diffusion electrode, and a catalyst coated electrolyte membrane (CCM). In general, the CCM is prepared by respectively transferring a cathode catalyst layer and an anode catalyst layer to opposite surfaces of an electrolyte membrane.
In this transferring process, respective catalyst layers are formed by transferring a catalyst layer forming composition which is doped and dried on a polymer film, such as polyethyleneterephthalate (PET) or KAPTON, to an electrolyte membrane using a hot pressing process. The hot pressing process results in many micro cracks in the transferred catalyst layers because the electrolyte membrane and the catalyst layers are in different states before and after the transferring process.
Such micro cracks lead to high resistance between the catalyst layers and the electrolyte membrane and high crossover of methanol to the cathode electrode, thereby degrading the performance and long-term stability of the electrolyte membrane-electrode assembly.